4 weeks of pregnancy is the time normally starts from Physiology. If people are waiting for the baby, "did you mean!?" With anticipation and anxiety, ドキドキ mind it might be.
4 weeks of pregnancy, is the time when menstruation begins, if always. Anyone who is waiting for a baby, you will time the heart-pounding anxiety and expected "!? Did you mean".
Four weeks of pregnancy, which is always starting time. For those of you who have been waiting for a baby, and possibly in expectation and anxiety that the mind does ドキドキ.